RITA Is Expressed in Trophoblastic Cells and Is Involved in Differentiation Processes of the Placenta

Involvement of RBP-J interacting and tubulin-associated protein in the distribution of protein regulator of cytokinesis 1 in mitotic spindles

The protein regulator of cytokinesis 1 (PRC1) is a key regulator of microtubule crosslinking and bundling, which is crucial for spindle formation and cytokinesis. RITA, the RBP-J interacting and tubulin-associated protein, is a microtubule associated protein. We have reported that RITA localizes to mitotic spindles modulating microtubule dynamics and stability as well as to spindle poles affecting the activity of Aurora A. As defective chromosome congression and segregation are the most remarkable features of cells depleted of RITA, we aimed to explore further potential related mechanisms, using various cellular and molecular techniques, including clustered regularly interspaced short palindromic repeats technique/deactivated CRISPR-associated protein 9 (CRISPR/dCas9), mass spectrometry, confocal microscopy, immunofluorescence, immunoprecipitation and Western blot analysis. Here, we show that FLAG-RITA precipitates PRC1 and tubulin, and that these two proteins co-localize in the central region of the central spindle. Reduction of RITA enlarges the staining area of PRC1 in mitotic spindles as well as in the central spindle. Its suppression reduces the inter-centromere distance in metaphase cells. Interestingly, microtubule bundles of the central spindle are often less organized in a non-parallel pattern, as evidenced by increased angles, relative to corresponding separating chromosomes. These data suggest a novel role for RITA in mitotic distribution of PRC1 and that its deregulation may contribute to defective chromosome movement during mitosis. As both RITA and PRC1 are closely associated with malignant progression, further work is required to elucidate the detailed molecular mechanisms by which RITA acts as a modulator in central spindle formation and cytokinesis.

HDAC2-mediated proliferation of trophoblast cells requires the miR-183/FOXA1/IL-8 signaling pathway

Pre-eclampsia (PE) is a major cause of maternal and perinatal death. Previous research has indicated the role of histone deacetylase 2 (HDAC2) in the pathogenesis of PE but the relevant molecular mechanisms are unknown. However, there is hitherto little information concerning the molecular mechanism behind HDAC2 in PE. Herein, we hypothesized that HDAC2 promotes trophoblast cell proliferation and this requires the involvement of microRNA-183 (miR-183), forkhead box protein A1 (FOXA1), and interleukin 8 (IL-8). We collected placental specimens from 30 PE affected and 30 normal pregnant women. HDAC2 and FOXA1 were poorly expressed while miR-183 and IL-8 were highly expressed in placental tissues in PE. In vitro, HDAC2 overexpression enhanced the proliferation, migration, and invasion of human trophoblast cells HTR-8/SVNEO. HDAC2 inhibited the expression of miR-183 by diminishing H4 acetylation in the miR-183 promoter region. miR-183 inhibition by its specific inhibitor increased the expression of FOXA1 and thus enhanced HTR-8/SVNEO cell proliferation, migration, and invasion. FOXA1, a transcriptional factor, enhanced HTR-8/SVNEO cell proliferation, migration, and invasion by inhibiting the transcription of IL-8. We also observed HDAC2 knockdown was lost upon FOXA1 overexpression, suggesting that HDAC2 could promote HTR-8/SVNEO proliferation, migration, and invasion through the miR-183/FOXA1/IL-8 pathway. In summary, the results highlighted the role of the HDAC2/miR-183/FOXA1/IL-8 pathway in PE pathogenesis and thus suggest a novel molecular target for PE.

The Function of Oncogene B-Cell Lymphoma 6 in the Regulation of the Migration and Invasion of Trophoblastic Cells

Human placentation is a highly invasive process. Deficiency in the invasiveness of trophoblasts is associated with a spectrum of gestational diseases, such as preeclampsia (PE). The oncogene B-cell lymphoma 6 (BCL6) is involved in the migration and invasion of various malignant cells. Intriguingly, its expression is deregulated in preeclamptic placentas. We have reported that BCL6 is required for the proliferation, survival, fusion, and syncytialization of trophoblasts. In the present work, we show that the inhibition of BCL6, either by its gene silencing or by using specific small molecule inhibitors, impairs the migration and invasion of trophoblastic cells, by reducing cell adhesion and compromising the dynamics of the actin cytoskeleton. Moreover, the suppression of BCL6 weakens the signals of the phosphorylated focal adhesion kinase, Akt/protein kinase B, and extracellular regulated kinase 1/2, accompanied by more stationary, but less migratory, cells. Interestingly, transcriptomic analyses reveal that a small interfering RNA-induced reduction of BCL6 decreases the levels of numerous genes, such as p21 activated kinase 1, myosin light chain kinase, and gamma actin related to cell adhesion, actin dynamics, and cell migration. These data suggest BCL6 as a crucial player in the migration and invasion of trophoblasts in the early stages of placental development through the regulation of various genes associated with the migratory machinery.

Primary Cilia in Trophoblastic Cells: Potential Involvement in Preeclampsia

The pathogenesis of preeclampsia, a pregnancy-related disease, is not completely understood. The primary cilium transduces a diverse array of signaling pathways important for vital cellular activities. Primary cilia were reported to facilitate trophoblastic cell invasion. We hypothesized their further functions in trophoblasts and were interested in related molecular mechanisms. We systematically examined the presence, length and percentage of the primary cilium, its mediated signal transduction, and its connection to trophoblast function. Various cellular and molecular methods were used including immunofluorescence staining, spheroid formation, gene analysis, invasion and tube formation assays with trophoblastic cell lines, primary trophoblasts, and placental tissues. We show that primary cilia are present in various trophoblastic cell lines derived from first trimester placentas. Cilia are also observable in primary trophoblasts, though in a small quantity. Importantly, primary cilia are shortened in trophoblastic cells derived from preeclamptic placentas. Mechanistically, interleukin-6, tumor necrosis factor-α or sera from patients with preeclampsia are able to reduce the length of primary cilia and impair the important sonic hedgehog signaling pathway. Functionally, trophoblastic cells with defective cilia display severe failures in their key functions, like migration, invasion and tube formation, also observed in trophoblastic cells depleted of the intraflagellar transport protein 88. This is accompanied by reduced gene expression of matrix metallopeptidases, vascular endothelial growth factor, and placental growth factor. This work highlights the significance of primary cilia in the functions of trophoblastic cells. Dysfunctional cilia may lead to compromised migration, invasion, and endothelial remodeling of trophoblastic cells, contributing to the development of preeclampsia.